An apparatus to modify a stomach wall comprises an elongated member including at least one lumen. A deployable member is coupled to the elongated member. The deployable member is configured to be advanceable and removable from the stomach in a non-deployed state and sized to be positioned in the stomach in a deployed state to engage at least portions of the stomach wall. The deployable member is further configured to house a fluidic media and at least portions of the deployable member wall is configured to be cooled by the fluidic media. The deployable member has a contour in the deployed state approximating at least a portion of a stomach. A microwave antenna is movably positioned in the deployable member so as to control a microwave field strength vector in relation to the antenna. The microwave antenna is configured to be coupled to a microwave energy source and deliver microwave energy to a selectable tissue site in the stomach wall while minimizing thermal injury to one of a mucosal or a submucosal layer. A cable member is coupled to the microwave antenna and is configured to be advanceable within the elongated member.